Breakless ignition system with means for preventing reverse engine operation

ABSTRACT

Disclosed herein is a breakerless ignition circuit for an internal combustion engine, which circuit includes trigger switch means, means for periodically conditioning the ignition circuit to obtain spark production in response to operation of the switch means, means for operating the switch means subsequent to previous conditioning of the ignition circuit by the periodic conditioning means, and in response to engine rotation in one direction when the piston is located relative to top dead center so as to obtain continued engine rotation in the one direction, and means for operating the switch means subsequent to previous conditioning of the ignition circuit by the periodic conditioning means and in response to engine rotation in the opposite rotative direction and when the piston is located so far in advance of top dead center so as to preclude continued engine rotation in the opposite direction. Also disclosed are means for preventing reconditioning or recharging of the ignition circuit for subsequent spark firing operation until well after the piston has passed top dead center so as to insure prevention of continued engine operation in the opposite direction.

United States Patent 11 1 Donohue et al.

[ Mar. 5, 1974 [75] Inventors: James A. Donohue, Milwaukee;

Harry S. Shore, Menomonee Falls,

both of Wis.

[73] Assignee: Outboard Marine Corporation,

Waukegan, Ill.

22 Filed: Dec. 16, 1971 [21] 'Appl. No.: 208,802

Primary Examiner-Laurence M. Goodridge Assistant Examiner-Ronald B. Cox

A210m2y,',1gen1, or firm-Michael, Best & Friedrich [5 7] ABSTRACT Disclosed herein is a breakerless ignition circuit for an internal combustion engine, which circuit includes trigger switch means, means for periodically conditioning the ignition circuit to obtain spark production in response to operation of the switch means, .means for operating the switch means subsequent to previous conditioning of the ignition circuit by the periodic conditioning means, and in response to engine rotation in one direction when the piston is located relative to top dead center so as to obtain continued engine rotation in the one direction, and means for operating the switch means subsequent to previous conditioning of the ignition circuit by the periodic conditioning means and in response to engine rotation in the opposite rotative direction and when the piston is located so far in advance of top dead center so as to preclude continued engine rotation in the opposite direction. Also disclosed are means for preventing reconditioning or recharging of the ignition circuit for subsequent spark firing operation until well after the piston has passed top dead center so as to insure prevention of continued engine operation in the opposite direction.

11 Claims, 6 Drawing Figures BREAKLESS IGNITION SYSTEM WITH MEANS FOR PREVENTING REVERSE ENGINE OPERATION BACKGROUND OF THE INVENTION The invention relates generally to internal combustion engines and more particularly to ignition systems for internal combustion engines. Still more particularly, the invention relates to ignition systems arranged to prevent reverse engine operation. Although various of the features of the invention are applicable to multicylinder engines, the invention will generally be described in connection with a single cylinder engine.

Breakerless ignition systems for internal combustion engines have been known for some time and generally constitute prior art. Such systems generally include switch means operable in response to engine rotation to cause the production of a spark which is effective to continue engine operation. In the past, such ignition systems have been disadvantageously capable of supporting engine operation in both rotative directions.

For example, there is shown in FIGS. 1 and 3 a typical prior art ignition system arrangement for triggering an ignition circuit (not shown) to produce a spark. The trigger arrangement 11 shown in FIG. 1 includes a trigger coil 13 which is supported around a coil core 17 and which is suitably stationarily mounted on an engine (not shown) by a bracket 19, together with a magnet 21 rotatable in a path which is in close proximity to the radially outer end of the coil core 17. Various magnet arrangements can be employed and can be mounted on any rotatable member. In the arrangement shown in FIGS. 1 and 3, the magnet 21 is mounted on a flywheel 22 and is of ceramic construction including two oppositely polarized magnet sections 23 and 27 separated by a non-magnetized or non-polarized interface 29. The magnetic section 23 is polarized so that the inner magnet surface 31 constitutes a north pole and so that the outer magnet surface 33 constitutes a south pole. The other magnet section 27 is oppositely polarized and each of the magnet sections 23 and 27 has an arcuate extent of about whereby the magnet 21 has an over-all arcuate extent of about 80.

The trigger coil I3 is mounted on the engine such that when the magnet 21 is rotating in the clockwise direction as shown by the arrow 37 in FIG. 1, the outer or leading end 39 of the magnet section 23 passes the coil core 17 when the engine piston (not shown) is located at approximately 35 prior to its top dead center position.

' Rotation of the magnet 21 past the coil core 17 will cause voltage generation in a pattern 43 generally as shown in FIG. 2 (In FIG. 2, the horizontal base line 47 represents time or angular flywheel motion which increases from the left to the right and the vertical scale represents voltage with one polarity--arbitrarily referred to as positive polarity--increasing from zero in the upward direction from the horizontal base line 47, and with voltage of the other polarity--referred to as negative--increasing from zero in the downward direction from the horizontal base line 47). Thus, as shown in FIG. 2, rotation of the magnet 21 past the coil core 17 causes initial generation of an initial pulse 49 of positive polarity when the piston is at about 35 before top dead center (T.D.C.) and as the leading end 39 of the magnet 21 passes the coil core 17 and causes a substantial change in flux in the coil core 17. When the nonmagnetized interface 29 passes the coil core 17 (40 later or when the piston is at about 5 after top dead center), the flux seen by the coil core 17 changes rapidly and a pulse 51 of opposite or negative polarity occurs. Subsequently, when the other end 53 of the magnet 21 passes the coil core 17, there occurs in the coil core 17 another flux change which produces a pulse 57 of positive polarity.

While other arrangements are also positive, it is intended that the ignition circuit controlled by the trigger coil 13 includes switch means (not shown in FIGS. 1 and 3) which is operable to cause spark generation upon the application of a positive pulse, and which is inoperative to cause spark generation upon the application of a negative pulse.

Thus, under normal operating conditions, the positive pluse 49 generated at approximately 35 before top dead center will cause the generation of a spark which will be effective to continue engine operation in the clockwise direction. The pulses 51 and 57 nor'mally will not produce spark generation in the arrangement contemplated by the FIGS. 1 and 3 construction.

The trigger arrangement 11 shown in FIGS. 1 and 3 is also disadvantageously effective to cause continued engine operation in the opposite or reverse rotative direction in the event, as sometimes will occur, of initial engine operation in the reverse direction. In FIG. 3, reverse or counterclockwise rotation of the magnet 21 is shown by the arrow 61. The voltage pattern 63 generated in the trigger coil 13 during reverse rotation is shown in FIG. 4. In this regard, an initial negative pulse 67 is produced at about 45 before the piston arrives at top dead center and when the end 53 of the magnet 21 passes the coil core 17 and causes a substantial change in flux in the coil core 17. As already indicated, a negative pulse does not produce ignition circuit operation. Upon further counterclockwise rotation of the magnet 21, the non-magnetized interface 29 passes the coil core 17 causing a rapid change in flux in the coil core 17 and producing a positive pulse 69 which occurs when the piston is about 5 before top dead center. The pulse 69 will cause ignition circuit operation to disadvantageously continue engine rotation in the reverse or counterclockwise direction. Subsequently, when the end 39 of the magnet 21 passes the coil core 17, another major flux change takes place in the coil core 17,

causing the production of another negative pulse 71 y when the piston is approximately 35 past or after top dead center. As already indicated, a negative pulse is ineffective to cause engine circuit operation.

Thus, the arrangement shown in FIGS. 1 and 3 is disadvantageously effective to continue engine operation in either direction depending upon the rotational direction occurring at the time of initial engine operation.

SUMMARY OF THE INVENTION The invention provides means for operating the trigger switch of a breakerless ignition system subsequent to conditioning of the ignition system for spark generation in response to such trigger switch operation, and in response to initial engine rotation in an undesired direction so as to produce a premature spark when the piston is so far spaced or in advance of top dead center position so as to preclude continued engine rotation in the undesired direction.

The invention also provides means operating in conjunction with the means referred to in the preceding 3 paragraph for preventing re-conditioning of the ignition system for further sparking operation during the interval commencing with premature spark generation and continuing until after the piston has traveled well beyond top dead center or beyond any possible occurrence of another triggering signal effective to fire the engine so as to continue operation in the undesired direction.

In the specifically illustrated embodiment of the invention, the means for preventing continued engine rotation in the undesired direction comprises a shoe which extends from a trigger coil in the direction counter to the direction of undesired rotation through an angular distance effective to cause premature spark generation in response to initial unwanted engine rotation at a time when such spark generation will be ineffective to provide for continued engine rotation in the unwanted direction. In the specifically illustrated embodiment, the shoe extends approximately 55 from the trigger coil and is effective to cause spark generation when the piston is at about 100 in advance of top dead center.

Also in the disclosed embodiment of the invention, the means for preventing further conditioning of the ignition system for spark generation after occurrence of the premature spark comprises a charge coil which is operative to charge a capacitor in response to engine rotation and which is located so that capacitor charging takes place only when the piston is substantially distant from top dead center and preferably adjacent to bottom dead center. Thus, there can be no recharging of the capacitor after the premature sparking until after the piston has traveled well past top dead center.

One of the principal objects of the invention is the provision of a breakerless ignition system which includes means for preventing reverse engine operation.

Another of the principal objects of the invention is the provision of a breakerless ignition system operative to prevent engine rotation in an undesired direction and including a triggering switch which, when the engine is rotating in the undesired direction, causes the generation of a premature spark upon initiation of unwanted rotation and at a time prior to when such a spark would be effective to continue rotation in the un desired direction and which system is thereafter operative to prevent further spark generation until after the piston has traveled past top dead center.

Another of the principal objects of the invention includes the provision of a breakerless ignition system which includes provision for preventing engine rotation in an unwanted direction without adversely affecting ignition operation in the other direction, which is economical to manufacture and construct, and which will provide reliable service over a long and useful life.

Other objects and advantages of the invention will become known by reference to the following description and the accompanying drawings.

DRAWINGS FIG. I is a fragmentary schematic view of a trigger arrangement in accordance with the prior art.

FIG. 2 is a schematic view of the voltage generated by the trigger arrangement shown in FIG. 1 when rotating in the direction of the arrow 37.

FIG. 3 is a view similar to FIG. 1 showing the triggering arrangement of FIG. 1 ma different position and in connection with reverse or unwanted rotation.

FIG. 4 is a schematic view of the voltage generated by the trigger arrangement shown in FIG. 3 in response to such unwanted rotation.

FIG. 5 is a fragmentary schematic view of an engine ignition system embodying various of the features of the invention.

FIG. 6 is a schematic view of the voltage generated by the trigger arrangement of the ignition system shown in FIG. 5.

Before explaining the invention in detail, it is to be understood that the invention is not limited in its application. to the details of construction and arrangement of parts set forth in the following general description or illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

GENERAL DESCRIPTION Shown in FIG. 5 is an ignition system including various of the features of the invention. The ignition system 75 includes an ignition circuit 77 including the previously described trigger coil 13 which is located relative to the previously described magnet 21 in the same manner as described in the section entitled Background of the Invention.

In accordance with the invention, there is also provided means cooperating with the trigger coil 13 and with the magnet 21 for generating a pulse in the trigger coil 13 which will be effective, upon initial rotation of the magnet 21 in the counterclockwise direction as disclosed by the arrow 79, to discharge the ignition circuit 77 at a time when the piston (not shown) is so far spaced from the top dead center position as to preclude continued engine operation in the counterclockwise direction.

Also in accordance with the invention, means are provided for preventing reconditioning or recharging of the ignition circuit 77 for subsequent spark firing operation until well after the piston has passed top dead center so as to insure prevention of continued engine operation in the counterclockwise direction.

Various ignition circuits can be employed. In the construction disclosed in FIG. 5, the circuit 77 is a typical capacitor discharge circuit including a capacitor 81 connected through a diode 83 to a charge coil 87 and to the primary coil 89 of an ignition coil 91 through an electronic trigger switch, such as an SCR 93 which includes a gate 97 connected to the trigger coil 13 and which is effective, upon application to the gate 97 of a positive pulse or current, to cause discharge of the capacitor 81 to the primary coil 89 of the ignition coil 91. As is also conventional, the ignition coil 91 also includes a secondary coil 99 connected to a spark plug 101. In addition to being connected to the gate 97, the trigger coil 73 is, at its other end, grounded as indicated at 103.

In accordance with the invention, the means cooperating with the trigger coil 13 and with the magnet 21 for generating in the trigger coil 13 a positive pulse which occurs upon initiation of rotation in the counterclockwise direction, i.e., substantially immediately at the beginning of counterclockwise rotation, and which is effective to discharge the circuit 77 so as to prevent continued engine operation in the counterclockwise direction, includes a shoe 105 which projects from the coil core 17 on the side of the coil 13 remote from the magnet 21 and which extends in the clockwise direction from the coil core 17 to a location adjacent to the path of the magnet 21. Assuming reverse rotation the shoe extends so as to cause generation of a spark at a time when the piston is located well in advance of top dead center. Preferably, the shoe extends so that a spark is produced when the piston is at least about 60 in advance of top dead center position. In the illustrated construction, the shoe extends for about 55 from the trigger coil 13 in the clockwise direction so as to cause spark generation, as will be further explained, when the piston is at about 100 before top dead center.

Preferably as-shown in FIG. 5, the shoe 105 comprises an integral part of the bracket 19 which supports the trigger coil 13 on the engine and includes, at the outer end thereof, a reversely bent ear or tab 107 having a surface 109 in more or less parallel relation to the path of the magnet 21. The shoe 105 is fabricated of flux conducting material and, accordingly, provides a flux path from the path of the magnet 21 to the radially inner end of the trigger coil core 17.

In operation, when the magnet 21 is rotating in the counterclockwise direction, as shown by the arrow 79 in FIG. 5, an initial portion 111 ofa pulse pattern 113, as shown in FIG. 6, will be produced incident to travel of the magnet 21 past the shoe 105 and past the coil core 17. Specifically, approach of the end 53 of the magnet 21 toward the bent end or ear 107 of the shoe 105 will cause increasing flux travel through the shoe 105 to the rear of the coil core 17, thereby causing generation ofa positive pulse or voltage 115 in the trigger coil 13, which pulse is of sufficient magnitude to trigger the SCR 93 and cause discharge of the capacitor 81 at a time when the piston is about 100 before top dead center.

Discharge of the capacitor 81 and generation of a spark at this time will not, under ordinary circumstances, cause firing of the engine. The subsequent compression occurring as the piston approaches top dead center will normally substantially slow or stop piston travel before top dead center, thereby, in any event, preventing continued engine operation.

In the event of absence of compression in the cylinder, rotation of the magnet 21 past the shoe 105 and the coil core 17 will complete the pattern 113 shown in FIG. 6. In this regard, continued rotation of the magnet 21 would generate a negative pulse as the nonmagnetized interface 29 passes the end 107 of the shoe 105 when the piston is about 60 before top dead center. A further positive pulse 119 would be generated when the magnetic interface 29 passes the coil core 17 when the piston is approximately at 5 before top dead center and a still further negative pulse would be generated as the magnet end 39 passes the coil core 17 when the piston is approximately 35 after top dead center. It is noted that when the magnet section 23 is passing the shoe 105, the othe magnet section 27 also is passing the coil core 17, thus providing a complete magnetic circuit through the coil core 17 and the shoe 105 between the magnet sections 23 and 27.

As already indicated, means are also provided for preventing recharging of the capacitor during the interval commencing with discharge of the capacitor 81 when the piston is at about 100 before top dead center and until .after the time when the pulse 119 would be generated or until after travel of the piston well beyond top dead center. While other arrangements are possible, in the disclosed construction, the charge coil 87 is located relative to the path of travel of the magnet-21 so that the travel of the magnet 21 past the charge coil 87 will effect charging of the capacitor 81 when the piston is close to bottom dead center and so that charging of the capacitor 81 will not occur when the magnet 21 is traveling in the counterclockwise direction during the interval occurring commencing with discharge of the capacitor 81 when the piston is about before top dead center and until piston travel from a position well past top dead center. It is noted that the location of the charge coil permits charging of the capacitor 81 during each cycle of clockwise rotation at a time prior to capacitor discharge when the piston is at about 35 before top dead center as explained in connection with FIG. 1, thereby to provide for continued normal engine operation in the clockwise direction.

While the disclosed arrangement employs the same magnet for charging the capacitor and generating a pulse which effects discharge of the capacitor, separate magnets could be employed for respectively charging and discharging the capacitor. In addition, the capacitor could be periodically-charged by means other than a magnet. Still further and in addition, the invention is not limited to capacitor discharge ignition systems but extends to all breakerless ignition systems which are electronically triggered. Still further, as already indicated, various of the features of the invention can be employed with multi-cylinder engines.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. A breakerless ignition circuit for an internal combustion engine having a piston, said circuit including trigger switch means, means for periodically conditioning said ignition circuit to obtain spark production in response to operation of said trigger switch means and including a charge coil and a magnet, said coil and magnet being mounted for relative rotation in response to engine operation so as to generate a potential in said charge coil, means including a trigger coil and said magnet for operating said trigger switch means subsequent to previous conditioning of said ignition circuit by said periodic conditioning means and in response to rotation of said engine in the forward rotative direction and when said piston is located relative to top dead center so as to obtain continued forward engine rotation, a flux conducting shoe extending from said trigger coil in the direction counter to reverse engine rotation and positioned to cut the flux path of said magnet, said shoe being operative during initial reverse engine operation to cause the trigger coil to operate the trigger switch means so far in advance of top dead center as to preclude continued reverse engine operation, said means for periodically conditioning said ignition circuit being inoperative during reverse engine rotation subsequent to gperation of said trigger switch means and prior to arrival of said piston at top dead center.

2. An ignition circuit for an internal combustion engine having a piston, including a magnet mounted for rotation about an axis in relation to movement of the piston, a spark plug, a charging circuit having a charging coil mounted adjacent the rotational path of the magnet whereby the charging circuit is charged before the desired ignition time,

trigger switch means operative to cause discharge of the charging circuit to fire the spark plug in response to a control signal,

a trigger coil mounted adjacent the rotative path of said magnet to generate a control signal in response to passage of the magnetic flux of said magnet,

the angular relationship of both coils relative to the axis of magnet rotation and to the angular embrace of said magnet being so related so as to produce a control signal and thus fire the spark plug a desired number of degrees in advance of top dead center when the engine is rotating in its normal direction to thereby sustain engine operation,

aflux conducting shoe extending from the triggercoil in a direction opposite reverse rotation of. the engine and having a portion adjacent the path of the magnet of sufficient mass to induce a control signal during initial reverse engine ro-: tation to tire the spark plug so far in advance of the piston reaching top dead center as to preclude; sustaining operation of the. engine in reverse. I

3. An ignition circuit according to claim 2 in which the angular relationship of the coils precludes rechargn he arges.s ssitipb qen 9 firinsth ep plug during reverse engine rotation andprior to the piston reaching top dead center.

4. A breakerless ignition circuit in accordance with claim 1 whcreinsaid shoe extends so as to cause generation of a spark when the piston is at least about 60 before top dead center in reverse engine rotation.

5. A breakerless ignition circuit in accordance with claim 1 wherein said shoe extends for about 55 from said trigger coil in the direction opposite to the reverse engine rotation direction and wherein said trigger coil is located relative to said magnet and to said piston so as to produce a spark when the piston is at about 100 before top dead center when said engine is rotating in said reverse direction.

6. An ignition system for an internal combustion engine including a piston reciprocable relative to a top dead center position, said ignition system comprising a breakerless ignition circuit including a charge coil, trigger switch means operable to cause discharge of said charge coil to produce a spark to fire the engine, a trigger coil electrically connected to said trigger switch means and operable to cause said switch means to discharge said charge coil in .response to the generation of a pulse in said trigger coil, a magnet, means mounting said charge coil, said trigger coil and said magnet relative to the piston and for rotation of said magnet in response to engine rotation relative to said charge coil and said trigger coil so as sequentially to charge said charge coil and to generate a pulse in said trigger coil during rotation of said magnet relative to said charge coil and said trigger coil in one rotative direction, and means cooperating with said trigger coil and with said magnet for generating a pulse in said trigger coil in response to initial rotation of said magnet relative to said trigger coil in the opposite rotative direction and when the piston is located in a position so far in advance of the top dead center 'position such that effective firing of the engine to continue rotation of said magnet relative to said trigger coil in said opposite rotative direction is prevented.

7. An ignition system in accordance with claim 6 wherein said ignition circuit comprises a apacitor et! wa rets iyeqirsai electrically connected to said switch means and to said charge coil and wherein said charge coil is located for charging of said capacitor when said trigger coil and said magnet are rotating relative to each other in the opposite rotative direction at a time other'than when the piston is gaveling from said piston position to the top dead center position. 8. An ignition system in accordance with claim 6 when said trigger coil and said magnet are rotating relative to each other in the opposite rotative direction and the piston is traveling from said piston position to the top dead center position.

9. A breakerless ignition system in accordance with claim 6 wherein said means cooperating with said trigger coil and with said magnet so as to prevent continued rotation in said opposite rotative direction comprises a flux conducting shoe extending from said trigger coil in the direction counter to said opposite rotative direction to adjacent to the path of said magnet.

10. A breakerless ignition system in accordance with claim 9 wherein said shoe extends so as to cause generation of spark when the piston is at least about 60 before top dead center.

1 l. A breakerless ignition system in accordance with claim 9 wherein said shoe extends for about 55 from the g er nth d re pnqsitst t e pos e rotative direction and wherein said trigger coil is located relative to said magnet and to said piston so as to produce a spark when the piston is at about before top dead center when said magnet is rotating 

1. A breakerless ignition circuit for an internal combustion engine having a piston, said circuit including trigger switch means, means for periodically conditioning said ignition circuit to obtain spark production in response to operation of said trigger switch means and including a charge coil and a magnet, said coil and magnet being mounted for relative rotation in response to engine operation so as to generate a potential in said charge coil, means including a trigger coil and said magnet for operating said trigger switch means subsequent to previous conditioning of said ignition circuit by said periodic conditioning means and in response to rotation of said engine in the forward rotative direction and when said piston is located relative to top dead center so as to obtain continued forward engine rotation, a flux conducting shoe extending from said trigger coil in the direction counter to reverse engine rotation and positioned to cut the flux path of said magnet, said shoe being operative during initial reverse engine operation to cause the trigger coil to operate the trigger switch means so far in advance of top dead center as to preclude continued reverse engine operation, said means for periodically conditioning said ignition circuit being inoperative during reverse engine rotation subsequent to operation of said trigger switch means and top dead center.
 2. An ignition circuit for an internal combustion engine having a piston, including a magnet mounted for rotation about an axis in relation to movement of the piston, a spark plug, a charging circuit having a charging coil mounted adjacent the rotational path of the magnet whereby the charging circuit is charged before the desired ignition time, trigger switch means operative to cause discharge of the charging circuit to fire the spark plug in response to a control signal, a trigger coil mounted adjacent the rotative path of said magnet to generate a control signal in response to passage of the magnetic flux of said magnet, the angular relationship of both coils relative to the axis of magnet rotation and to the angular embrace of said magnet being so related so as to produce a control signal and thus fire the spark plug a desired number of degrees in advance of top dead center when the engine is rotating in its normal direction to thereby sustain engine operation, a flux conducting shoe extending from the coil in a direction opposite reverse rotation of the engine and having a portion adjacent the path of the magnet of sufficient mass to induce a control signal during initial reverse engine rotation to fire the spark plug so far in advance of the piston reaching top dead center as to preclude sustaining operation of the engine in reverse.
 3. An ignition circuit according to claim 2 in which the angular relationship of the coils precludes recharging the charging circuit subsequent to firing the spark plug during reverse engine rotation and the piston reaching top dead center.
 4. A breakerless ignition circuit in accordance with clAim 1 wherein said shoe extends so as to cause generation of a spark when the piston is at least about 60* before top dead center in reverse engine rotation.
 5. A breakerless ignition circuit in accordance with claim 1 wherein said shoe extends for about 55* from said trigger coil in the direction opposite to the reverse engine rotation direction and wherein said trigger coil is located relative to said magnet and to said piston so as to produce a spark when the piston is at about 100* before top dead center when said engine is rotating in said reverse direction.
 6. An ignition system for an internal combustion engine including a piston reciprocable relative to a top dead center position, said ignition system comprising a breakerless ignition circuit including a charge coil, trigger switch means operable to cause discharge of said charge coil to produce a spark to fire the engine, a trigger coil electrically connected to said trigger switch means and operable to cause said switch means to discharge said charge coil in response to the generation of a pulse in said trigger coil, a magnet, means mounting said charge coil, said trigger coil and said magnet relative to the piston and for rotation of said magnet in response to engine rotation relative to said charge coil and said trigger coil so as sequentially to charge said charge coil and to generate a pulse in said trigger coil during rotation of said magnet relative to said charge coil and said trigger coil in one rotative direction, and means cooperating with said trigger coil and with said magnet for generating a pulse in said trigger coil in response to initial rotation of said magnet relative to said trigger coil in the opposite rotative direction and when the piston is located in a position so far in advance of the top dead center position such that effective firing of the engine to continue rotation of said magnet relative to said trigger coil in said opposite rotative direction is prevented.
 7. An ignition system in accordance with claim 6 wherein said ignition circuit comprises a capacitor electrically connected to said switch means and means connected to said capacitor for charging of said capacitor when said trigger coil and said magnet are rotating relative to each other in the opposite rotative direction at a time other than when the piston is traveling from said piston position to the top dead center position.
 8. An ignition system in accordance with claim 6 wherein said ignition circuit comprises a capacitor electrically connected to said switch means, a charge coil electrically connected to said capacitor, and means mounting said charge coil and said magnet relative to the piston and for rotation relative to each other in response to engine rotation for charging said capacitor except when said trigger coil and said magnet are rotating relative to each other in the opposite rotative direction and the piston is traveling from said piston position to the top dead center position.
 9. A breakerless ignition system in accordance with claim 6 wherein said means cooperating with said trigger coil and with said magnet so as to prevent continued rotation in said opposite rotative direction comprises a flux conducting shoe extending from said trigger coil in the direction counter to said opposite rotative direction to adjacent to the path of said magnet.
 10. A breakerless ignition system in accordance with claim 9 wherein said shoe extends so as to cause generation of spark when the piston is at least about 60* before top dead center.
 11. A breakerless ignition system in accordance with claim 9 wherein said shoe extends for about 55* from the trigger coil in the direction opposite to the opposite rotative direction and wherein said coil is located relative to said magnet and to said piston so as to produce a spark when the piston is at about 100* before top dead center when said magnet is rotating in said opposite rotative direction. 